Postfix 2.5.3 has just been released and I just installed and tested it on my test server. There are no major changes in this release just some bugfixes. If you haven’t experienced any problems there is no pressure to upgrade.

Cleanup: a poorly-implemented integer overflow check for
TCP MSS calculation had the unexpected effect that people
broke Postfix on LP64 systems while attempting to silence
a compiler warning. File: util/vstream_tweak.c.